The invention relates in general to a method and apparatus for characterizing gastrointestinal sounds and in particular to a method and apparatus employing a microphone array attachable to a patient""s body for collecting sounds from multiple sources in the body and a computer system for receiving digitized gastrointestinal sound signals and determining the spectra and duration of the sounds and characterizing states of the gastrointestinal tract on the basis of the spectrum and duration.
It has been known in the past to employ electronic analysis of sounds from the gastrointestinal tract as an adjunct to the physician auscultating the gastrointestinal tract in an attempt to determine quickly and with a minimum of diagnostic equipment the condition of the patient. In the past, for instance, as disclosed in U.S. Pat. No. 5,301,679, a method and system was provided for providing diagnostic information for various diseases including diseases of the gastrointestinal tract by capturing body sounds in a microphone placed on the body surface or inserted orally or rectally into the gastrointestinal tract. The spectrum analyzer used a real time audio one-third octave technique using a plurality of analog filters and a peak detector provide a log calculation of envelope amplitudes. Other systems also used microphones sensitive to specific frequency ranges and are exemplified by Dalle, et al. xe2x80x9cComputer Analysis In Bowel Sounds,xe2x80x9d Computers in Biology and Medicine Feb. 4(3-4), 1975 pp. 247-254; Sugrue et al., xe2x80x9cComputerized Phonoenterography: The Clinical Investigation of the New System,xe2x80x9d Journal of Clinical Gastroenterology, Vol. 18, No. 2, 1994, pp. 139-144; Poynard, et al., xe2x80x9cQu""attendre des systemes experts pour le diagnostic des troubles fonctionnes intestinaux,xe2x80x9d Gastroenterology Clinical Biology, 1990, pp. 45C-48C. Also of interest are U.S. Pat. Nos. 1,165,417; 5,010,889; 4,991,581; 4,792,145. Unfortunately, none of the systems relate to using specific morphological filtering an event characterization of the type which might be able to identify ileus or small bowel obstruction or the like. The prior systems seem to have suffered from the inability to cope with relatively irregular sounds and irregular signals and to pick events of detail from the signal. Many of the systems used averaging techniques on the raw signal, which would tend to obscure the event of interest in noise or other unwanted portions of the signal and thus actually work against the diagnostician attempting to characterize genuine gastrointestinal sounds as opposed to other sounds coming form the body. Thus, it would appear that despite the use of sophisticated spectral techniques and the like the prior art, having been unable to identify events, appeared to operate on relatively noisy data from which it would be difficult to extract meaningful conclusions. Accordingly, what is needed is a system which can quickly and easily identify such conditions.
The invention is directed to a method and apparatus including a microphone array including three microphones fixed on a mount for precise positioning with respect to key location of the anatomy of the patient with a fourth free microphone which may be placed adjacent to the sternum of the patient for picking up breathing, cardiac and environmental sounds and the like which are to be subtracted from the gastrointestinal sounds and are treated as noise. The microphones feed a sound equalizing system for selection of certain sound frequency ranges which in turn feeds analog sound signals representative of gastrointestinal sounds to a tape recorder. The tape recorder is connectable to a computer which includes an analog to digital converter. Digitized multiple gastrointestinal sounds may then be processed by a computer in accordance with morphological filtering algorithms which characterize both the spectra and the duration of the sounds emanating from the gastrointestinal tract. In addition, the computer can subtract out components of sounds related to the background noise from the surrounding room or from the breathing which is picked up by a free microphone. An output indication may be provided to the physician or other health care worker through a printer or a video display screen which provides an indication as to the type of sound and a characterization in some cases as to the condition of the patient such as ileus and the like.
The present system is particularly characterized by the fact that the initial processing of the digitized audio signals relates to selecting gastrointestinal events of interest from extended noisy audio signals. One way in which this has been done in the present application is to use an amplitude thresholding system to look for events of interest and then to focus additional processing on those events. This approach does not appear to have been taken in the previous systems and may have reduced their ability to extract meaningful data from the relatively noisy environments in which they operate.
It is a principal aspect of the present invention to provide a gastrointestinal sound processing system which can characterize individual gastrointestinal events on diagnostic basis.
It is another aspect of the present invention for providing a gastrointestinal sound characterization system which intercepts sounds from multiple locations in the human body for diagnostic purposes.